Oxide semiconductor thin film transistor typified by IGZO TFT has been rapidly developed. In order to produce a higher resolution display panel, it is necessary to solve the problem of excessive parasitic capacitance of the TFT. Generally, a top-gate self-aligned TFT structure is used in the prior art to reduce the parasitic capacitance of the TFT. However, the display panel with top gate TFT structure has the following problems to be solved. In an aspect, [PPMH1]the electrical resistance between the active layer and the source and drain electrodes can be reduced. In another aspect, since the oxide semiconductor itself is sensitive to light, the electrical characteristics of the channel region will be changed under illumination. In a further aspect, due to the presence of the LDD region, the shielding layer are not able to completely and effectively isolate the influence of light on the active layer, so that the TFT is prone to threshold (Vth) drifting, and the TFT may still have such a problem of poor illumination stability.